Projector



Nov. 29, 1932. J, P|ERR0N 1,889,696

PROJECTOR Filed June 27, 1931 Patented Nov. 29, 1932 JACQUES PIERRON, OF VAUX-SUR-SEIN, FRANCE PATENT OFFICE PROJECTOR Application led J'une 27, 1931, Serial No. 547,318, and in France July 30, 1930.

The present invention has for its object a projector in which the emitted pencil of rays is limited in height in such a manner that the visual rays (rays of light from an object to the eye) situated above the Zone thus restricted, cannot penetrate into the interior of the projector. Automobile front lights equipped with my invention will permit not only the emission of a pencil of rays for the 19 purpose of lighting the road ahead, but they will also prevent the dazzling effects common in lamps which are not provided with a projector of the type described hereinafter.

The present invention consists in arranging before the projector tWo right angle prisms placed side by side along their inclined surface, one of them comprising an extension in a parallelepiped form enclosed vin an opaque sheath.

The invention consists also in the combination of such a system of prisms with a reflector having an ellipsoidal form, one of the focuses of which coincides with the luminous source and the other focus of which is in front of the projector and on the axis passing through the luminous source and forming a tangent represented on the' accompany-ing drawing wherein o Figure l is a view in longitudinal section of the said projector.

Figure 2 is a longitudinal section accord-y ing to X-Y of Figure l, and W Figure 3 is a. diagrammatical view of the prism with a parallelepiped base, in Which it may be seen that the luminous rays situated above the limited zone as specified at thebeginning of the specification, do not penetrate into the interior of the projector. n

Upon referring to Figures l and 2, it Will ,The reflector B is in the form of a seiiii-l j sphere Whose centre is at F1. i y The prisms C and D arearranged between the focuses F1 and F2. f

The upper prism C is arranged in such a manne-r that its inclined face fb coincides y With the axis my at the angle R of the total reflection or an angle close thereto. The face c?) is either flat, cylindrical or lenticular according to the lightingveffects desired. (In the construction described, the face ab has been given a concave lenticular form so as to carry over the focus F2 to F3, Which arrangement reduces theJ` dispersion of the pencil of rays.)

The lower prism D is arranged in such a manner that its face fb coincides With the axis my under the angle R vof the ytotal reflection or an angle close thereto; it is placed against the prism C along its liypotenuse surface. The prism D is extended in the form of a right parallelepiped abcd. The height ed of the parallelepiped is such that in the right section coed, an isosceles triangle 0M) may be inscribed, the angles of which, at the base, are e ual to the angle R of the total reflection. T e parallelepiped portion @bed is surrounded by an absorption sheath M.

It follows that if, in certain particular cases, it is considered unnecessary to entirely utilize the complete field of invisibility, the height of the parallelepiped may be diminished Without the device Lthereby leaving the limitsy of the present invention. It is sufficient that the parallelepiped may always be present and that the dimension defined be that which insures the greatest field of invisibility. .j

The operation of the projector is the following The rays received bythe spherical reflector B reflected on to the* focus F1 strike the rc` iiector A and combine with the rays received directly by this latter.

The ellipsoidal reflector A produces a semiconical pencil of rays which converges on 5 the focus F2 and which may or may not be carried over to the focus F3.

'Ilie pencil meets the prisms C and D.

The upper prism C compensates eXactly for the deviation and dispersion effects of 10 the prism D.

The lower prism D, due to its shape, constitutes an impenetrable screen for any visual ray emanating from any point whatever situated above the separation surfaceSS as indicated in Figure 3.

T he visual rays emanating from any point such as 'a' situated above the separation surface SS either strike the surface fb which reflects them on to the surface de like the the surface be directly like the ray l, or strike ray 2,01 strike the surface de which refiects them on to the surface be like the ray 3.

rI'he most extreme ray, that is, the ray closest to 0c is reflected.

Indiscriminately,all the rays issued from the point z must encounter the absorption sheath M. From the semi-conical form of the pencil, determined by the reflectors A. and B, it results that (a) the principal pencil of rays constituted by the cones of intense light issued from thelilament traverses the prisms without absorption of light, the rays of this pencil feriring a positive angle with the optical axis my.

lation concerning` either the angles, the edges,

or the exterior surfaces of the prisms, have no appreciable effect upon the working of the device.

rl`he precision of the device thus only depends upon the making of a true-plane glass face and mayV be obtained easily through means in current use in the industry.

(el) that it is possible to give the posterior surface ab of the upper prism C a cylindrical form andabove all a lenticular lform suitable to regulate the4 pencil in widthy and cipal pencil.

Vresults that rIhe total reiiection by the upper prism C is` depth without absorption of light of the prin- From the parallelepiped prolongation bode of the lower prism D there results:

(f) that a perfect screen impenetrable to any visual ray emanating from any point such as z' situated above the separation surfaces SS tangential to the principal pencil and containing the axis my of this pencil, is constituted.

From the whole of the device described, it

(g) ythe projector yemits a semi-conical pencil the widest and most luminous part of `which lights the most distant objects.

(it) the projector is entirely invisible to any eye placed at any point whatever of the space situated above a separation surface tangential to the principal pencil and containing the axis of this pencil.

V(i) this invisibility is obtained without absorption of light ofthe principal pencil.

(j) this invisibility is obtained even if the constituent parts are iniperfectly constructed or assembled, and on the only condition that ghe hypotenuse surfaces ofthe prisms are What I claim and desire to secure by Letters Patent of the United States is 1. In a headlight, a casing, a source of light therein, and means in front of said casing to propagate the light and to prevent dazzling),` said means comprising a pair of right angle prisms placed in juxtaposition along the inclined faces thereof, one of said prisms being provided with an extension of parallelepiped form, and an opaque sheath surrounding said extension.

y2. In combination With the structure described in claim l, a reiiector of ellipsoidal form in the casing,having one focus coinciding with the source of light and the other focus being forward of said reflector and upon an axis passing through the source of light and being tangent to the upper portion of the opaque sheath.'

3. In combination with the structure described in claim l, a reflector of ellipsoidal form in the casing, having one focus coinciding with the source of light and the other focus being forward ofsaid reflector and upon an axis passing through the source of light and being tangent to the upper portion of the opaque sheath, and a second refiector of spherical form whose center coincides with the said source oflight.

In testimony whereof I adir; my signature.

l aJACQUES PIERRON.

(e) that it is possible to prolong the lower' l prism D by means of a right angle parallele piped bode, sheathedy and .withoutabsorption l c5 of light from the principal pencil. i 

